The invention relates to testing a semiconductor wafer, and in particular to testing a Hall magnetic field sensor.
Magnetic fields are used for testing of semiconductor wafers, especially Hall magnetic field sensors, during a production test as part of the manufacturing process. Generating precise magnetic fields suitable for a test with commercially available mixed-signal testing systems is not possible without additional devices, so an additional and undesirable hardware expense is incurred. Since different magnetic field strengths are usually needed for a test, one must expect relatively long transient times for the coils producing them, or a complicated mechanical system. In addition, because the homogeneous region of the magnetic field produced in this way is relatively small, only a few sensors can be tested at the same time on a wafer.
Since a Helmholtz layout is not possible for the coils producing such a magnetic field for a wafer test with a thermochuck, one can only provide an inexact magnetic field for the testing or sampling. Such a thermochuck provides a desired wafer temperature, and the wafer lies on it over its entire surface. Currents flow in the thermochuck, generating disruptive magnetic fields. Furthermore, the thermochuck normally contains magnetic materials that distort the desired magnetic measuring field. In particular, for a Helmholtz layout one would require a coil in the thermochuck, which would be difficult to implement, so that in the final analysis there are many problems with magnetic measurements of a wafer in conjunction with a thermochuck.
There is a need for an improved technique of testing a semiconductor wafer such as a Hall effect sensor.